Facsimile synchronizing device



Dec. 27, 1949 A. G. COCJLEY FACSIMILE SYNCHRONIZING DEVICE Filed March12, 1948 INVENTOR.

Patented Dec. 27, 1949 2,492,621 FAG SIMILE SYNCHRONI-ZING DEV-ICEAustin G. Cooley, New York, N. Y., assignor to Times FacsimileGorporatiom'New York, ELY, a corporation of New York Application March12, 1948, Serial No. 14,456

'1 Claims. 1

This invention relates to telefacsimile apparatus and more particularlyto the motor drive and phasing mechanism employed for starting anddriving the drum or other scanning member in controlled speed and phaserelation.

One object of the invention is to provide an improved and eflicientfacsimile drive which is adapted to start a relatively large picturedrum or scanning member from rest, bring it into proper phaserelationship and rotating at a desired constant speed in synchronismwith the machine with which it is connected.

Another object of the invention is to provide an improved phasingmechanism for facsimile or telephoto apparatus in which the phasing loadon the motor is low. 7

Another object of the invention is to reduce the power required to drivethe scanning mechanism of a facsimile machine to a minimum.

A further object of the invention is to provide an improved drivearrangement for the picture or recording drum of apparatus of thecharacter described employing a driving motor of a nonsynchronous typeand a second motor of a synchronous type so interconnected that thedriven element rotates at a speed determined by the synchronous motor.

A still further object of the invention is to provide an improved drivearrangement for apparatus of the class described which is adapted tobring the driven element up to synchronous speed and eiiect a phasingoperation automatically in response to the closure of control switcheswithout requiring manipulative skill to start and phase the facsimileequipment.

Still another object of the invention is to provide driving mechanismfor the drum of a facsimile machine which will permit the drum to bestopped or held stationary during or after the phasing operation withoutlosing phasing adjustment.

Other objects and advantages of the invention will appear from thefollowing detailed description of the embodiment thereof shown in the 45accompanying drawings, wherein Fig. 1 is a perspective view, partly insection, of a preferred construction. In this view the element to bephased in its angular position and driven at constant speed is shown asa drum or cylinder of a facsimile machine.

Fig. 2 is a perspective view showing the ,relation of the driving andphasing elements of Fig. 1 in 'a-simp'lified and exploded form in orderto show more clearly the underlying principles of construction.

In'telefacs'imile apparatus in general use, picv ture transmitting andrecording drums are em-.

ployed which are driven at a constant speed and in a desired phaserelation. In this manner the drums of the transmitter and recorder areoperated in rotational synchronism and in phase. In some apparatus othertypes of scanning devices are employed instead of the drums, which arealso required to be operated in controlled speed and phase relation.

In order to maintain the drum or scanning member of the recorderoperating at the same speed as that of the transmitter, the respectivescanning members may be driven by synchronous motors, each controlled bya tuning fork or other frequency standard or connected to the samealternating-current system. Another synchronizingarrangement involvestransmission of a low-frequency carrier from the transmitting .stationto the receiving station and synchronizing the speeds of the two motorsby the carrier. In most synchronizing systems, the sychronous motor isdriven by a vacuum tube amplifier. Consequently it is desirable toreduce the size of the synchronous motor element as much as possible byreducing the load imposed thereon by the drum or scanning member.However, if the drum is started and stopped for phasing,

,usually a friction clutch is provided and considerably more power isrequired to prevent stalling the synchronous motor by the clutch loadthan for merely maintaining the operating speed of the drum. At thepresent time, facsimile equipment is being used which employs relativelylarge picture drums or rotating members driven at relatively high speedsand therefore requiring increased driving power.

It has been found impractical to connect these taining the drum orscanning member rotating through a secondary clutch or other auxiliarydrive means but the construction is rather com- .plicated, particularlyas it was necessary to insure 0 that the auxiliary cl-utchwould notdrive the drum at .a speed greater than synchronous speed or provide insome manner for bringing the drum.

tosynchronous speed.

. In accordance with theembodiment cf the vention'lllus'tra'ted, thesynchronous motor is con- It has been pro-- posed to reduce the :clutchfriction load by mainnected to a rotatable phasing member and a drivingconnection in the form of a latch is provided between the phasing memberand the drum so that the drum is coupled to the phasing member in onepredetermined angular position of the drum relative to said member.Further means is provided for overdriving the drum so that when thephasing member has been released or phased and is rotating atsynchronous speed, the drum will catch up to the phasing member androtate at the synchronous speed of said member with the driving loadtaken by the motor employed for overdriving the drum. The drivingconnection between the rotatable phasing member and the synchronousmotor or other constant-speed control member enables the phasing memberto be stopped for phasing without stalling the synchronous motor. Thisdriving connection is preferably of a type which positively controls thespeed of the phasing member without imposing more than a minimum load onthe synchronous motor. A variable speed motor may be employed foroverdriving the drum or the synchronous motor may be geared through adirect drive shaft to the drum with an interposed friction slip clutch.In accordance with a further feature of the invention, the synchronousmotor is preferably connected to the phasing member through a worm andworm gear of a type which prevents torque from the phasing memberoverdriving the synchronous motor above synchronous speed, such as anirreversible worm-gear drive or a worm-gear drive designed to limit thetorque applied to the synchronous motor shaft.

Referring to the drawing, the drum I of a facsimile machine is mountedon a shaft 2 for rotation at a constant speed during transmission. Thedrum I may be a picture drum of a facsimile transmitter, in case thetransmitter is phased with a remote recorder, or may be the recordingdrum of a recording facsimile machine where such recorder is phased witha remote transmitter. It is further understood that the drum I isintended to represent any rotatable scanning element of this characterwhich is to be controlled in speed and phase relation. The shaft 2 isshown as provided at the outer end thereof with a drive gear 3 meshingwith a drive pinion 4 for the purpose of starting the drum I from restand bringing it up to a desired rotative speed. A shaded-pole motor orother variable speed motor may be provided for overdriving the drumthrough the gears 3 and 4, or other suitable driving means may beprovided for initially accelerating the drum I and providing all or apart of the torque required for the driving load. An induction motorhaving a high slip-speed characteristic may be used as a drive motorsince it has a fairly constant torque over a considerable range ofspeed. 7 p

In order to control the speed and phase relation of the drum or scanningmember I, a rotatable phasing member 6 having a projecting lug I isprovided in the specific embodiment shown by way of illustration. Thephasing member 6 is coaxial with the drum or scanning member I, and maybe journaled on the shaft 2. The position of the phasing membermay becontrolled by a timed phasing current impulse, as shown for example inmy prior patent, No. 2,275,249 granted Mar. 3, 1942. In order to stopthe phasing member 6 in a predetermined phase relation (predeterminedangular position) and release the same in re- V sponse to the receipt ofa phasing pulse, means such as a pivoted latch memberQ controlled by 4an electromagnet 9 may be provided. As shown, the latch member 8 isdisposed in the path of the lug I and stops the rotation of the phasingmember 6 until the latch is retracted by energization of the magnet 9upon receipt of a phasing current pulse applied to the conductors ID.

The phasing member 6 is driven at a constant synchronous speed by meansdescribed hereinafter and serves to control the speed of the drum I bymeans of a phasing coupling means I2. In the embodiment shown, thecoupling means I2 is in the form of a latch operative to couple thescanning means I and phasing member 6 together in one relative angularposition of the two members. It preferably consists of a two-Waydouble-jointed latch pivoted on the scanning member and adapted toengage the lug I of the phasing member 6. As shown, the coupling meansI2 comprises a fixed base or supporting element I3 rotating with thedrum, a first pivoted latch member I4 and a second latch member I5pivoted on the member I4. The latches I 4 and I5 are arranged to pivotin opposite directions, as indicated by the arrows in Fig. 1. A strongspring I6 is interposed between the members is and I4 so that the latchcan tilt by the pivoting of the member I4 only in response to theapplication of considerable force. On the other hand a light spring I1is interposed between the members I4 and I5 so that the member I5 cantilt to permit the lug I of the phasing member 6 to pass the latch in aclockwise direction without imposing substantial drag on the phasingmember. Thus the phasing member 6, if driven at constant speed, willserve to hold the drum I at the same speed, through the couplingconnection I2 when thedrum is overdriven by the shaft 2. When the shafttends to run above synchronous speed, the connection I2 engages the lugI, the spring I 6 being sufficiently strong to prevent buckling of thelatch I3, I4 by the driving torque. However, if excessive torque isapplied between the drum I and the phasing member 6, either while thedrum is rotating or as a result of turning it by hand when the phasingmember 5 is stopped by the latch 8, the pivoting of the member I4 of thelatch will prevent damage to the coupling I2.

The rotative speed of the phasing member 6 is maintained at the constantsynchronous speed by means of a motor 2!; or in case a fluctuatingscanning speed is used, as explained for example in my prior Patent No.2,404,566, the motor 2! maintains synchronism of the member 6. The motor2! is preferably a synchronous motor which is synchronized with thedriving motor of the remote facsimile machine, as by means of atransmitted carrier or by the use of common or synchronized sources ofalternating current for driving the motors, as well known to thoseskilled in the art. As shown, the motor 2i is connected to the phasingmember 6 through a worm 22 and worm gear 23, the latter being connectedto a driving sleeve 24 surrounding the shaft 2. The

Worm gear 23 is shown as clamped to the sleeve 24 by a clamp 25. Thesleeve 26 in turn is keyed to a ratchet gear 26, the teeth of which areengaged by a pivoted pawl 21 on the phasing member 6, The pawl 27 ispivoted on a stud 28 and is urged by a spring 29 against thecircumference of the toothed ratchet gear 26. The

pawl and ratchet connection shown is provided for the purpose ofpermitting substantially free rotation of the synchronous motor rotorwhen i the phasing 'member 6 -is stopped without imparting a heavyfrictional drag on the Synchro aaamnar.

n'ous moron. while at: the same: time? the phasing members is positivelyheldbaels (to; synchro'e nous-ispeedf)" by the synchronous motor 2 It:When reieasem for rotatiom upon; the receipt of the phasingpulsccontroliing:the'latch 8:

=When -the phasingmembcr fi'is stopped by the latch 8, the motor" 24drives the? ratchet gear im a clockwise direction; the' pawl H slippingoverthe teeth inthe gear; When the phasingmembei 'B isreleasedrfor-rotation however, since:

thc f-riotion load is=sma ll thee pressure of: thepawlon; a teeth of thegear 26: is suffic'iently great toei'fect a ratherpositive: drive Ibetween the said-cgear and. the phasing:- member 6' on which the paw lis pivoted. In this manner the' phasing member is operatedat the:synchronous speed of tl' e drive shaft substantially instantaneouslyafter: thephasing pulse is receivedr- The driving power of the pawl= andratchet in this; direction? is determined by the shape: or thepawlandmatchet teeth and the pressure ofthe spring and thus is not avariablefactor like the: friction; drive of the slip clutchheretofore used.- Inthe opposite direction; when the over-drivetem'lsv to rotate the drumand phasing. member 6 above synchronous speed, the pawl and. ratchetteethare shapedto providepositive'torque transmission so. that. the'motor 2I- positively limits or retards the phasing. member to thedesired synchronous speed.

The general" principles, underlying the inven-- tion will bereadilyunderstood.- from the. simpli'fiedv drawing? of Fig. 2, whichillustratesthe essential relation between. the driving. phasing and scanningmembers of Fig. L in. a. simplified form. As. shown, referring to Fig. 2and usingcorrespondi-ngi reference characters. to. denote correspondingelements of the construction, the drum: l is. driven. throughthe shaft 2by overdrive'means operative to bring it up from rest to thedesiredspeed and tending to rotate the drum above synchronous speedl.Obviously, in stead of a separate induction or other" variable speed,motor; the" shaft 2 may be driven from the" synchronous motor 21 througha slip-friction clutch; The drum IE is maintained at constant speed bythe retarding force applied" through the coupling means I 2 and the lugI of the phasing member 6 which is driven at constant. of syn.-clironizecf speed by the. synchronous motor 2!.. Thus", when the drum Icatches up to the phasingfmember's iand the coupling; means I2 engagesthe" lug T, the drum is ret'arde'd" and constrained to operate at thesynchronous or controlled speed. of the phasing member" Iii The drivingconnection" consisting" of the pawl and ratchet 26, 2'! permits. thecontinued operation of the synchronous motor 21, when the phasing member6 is latch'ed? during the phasing" operation This is required becausethe drive for the phasing member must be: operating at synchronous speedat the instant the phasing member is released by the phasing pulse.However, the pawl and ratchet provide a. drive connection which has aminimum: frictional drag when the phasing member It is stopped, andwhich picks up the phasing mernber with. negligible slippagewhen it isreleased.

In accordance with another feature of the invention, the worm-gear drive22, 23 is designed to not only avoid undue loading of the synchronousmotor 2! by the drum drive but also limit the reverse torque on themotor tending to pull it out of synchronism. The friction between a wormand worm gear depends upon load and speed? well? as" the materiahandiprofiles or the described; the? helix angle or the thread (the angle ofthread with a: line' at right angles? to the axis of the worm) shouldbetor the order of 7 to 12 degrees. As noted, this angle for-"optimum:results will change for different materials, speeds; and so forth butimprovement Willi be obtained generally in th'e: stated rangefor' 'ordina'ry gear materialsr; Inf this manner, the size. of thesynchronoustmotor- 24' may be reduccd: to a minimumasince17h6:-$1'18;1li1lg and accelerat-- ing torques produced bytheoverdriveare smaliz.

I-n starting, and phasing- .the= drumi'or scanningmember' It, thecircuitof the synchronous motor 2|? is closedandrthe motor brought to synchrotnous speedv If, the, phasing member 6' is locked: by the phasing. latch=1-, the ratchetmechanism 26,.2-1 permitsethe synchronous motor-2drtopper ate at-synchronous speed without appreciable drag because of?-the locking. of the phasing. memeber 6. When thephasing.pulse-isreceived, the latchmember. 8 is retracted from thephasing lug, 1,. and the phasing member 6- rotateswith:

the ratchet gear 21 at synchronous speech. The drum is brought up tospeed by closing its a motor circuit,. either before or after phasing,and tends to rotate above synchronous speedr. When thedrum I catches upvto thephasing. member 5,. and the coupling. means I-2 engages the. mg Ioi said member,. the drum. I is retarded. by... the phasing member Iiand: continues to rotate in the desired phase relation and atsynchronousspeed Itwill be apparent that the invention-provides anefiective phasing. mechanism in which v a large high-speedscanningmember can be: brought to the desired phase relationwith a. phasing mem-'ber. controlled by the phasing. pulse, and v maintained at desiredsynchronous. speed. by means.- of asmallisynch'ronous motor.. Since theload.onthe synchronous. motor is small, even when the phasing member isstopped for. phasing. there is nov possibility of stalling. the motor;On the other hand, the relatively heavy power required to start and.rotate the drumor scanning member I is obtained? from. an auxiliarypower source which neednotibe closelyregulated as to speed, such as avariable-speed. shaded-pole motor.

It will also be noted that in case of a variable scanning speed'of'transmitter andrecorder, as employedinthe secrecy or scrambler equipmentdisclosed in my above-mentioned Patent No.

2,404,566,. the motor il 'when, synchronized with the, drivingmechanism'of the remote machine is adaptedito control therotationofth'e' drum I in accordance with variations in the-'rotativespeed of the motor. The driving mechanism according to the invention hasthe advantage that rapid, wide-range variations. in the speed of thescanning means may be controlled by a small motor 21' of" the"synchronous. type. The term synchronous speed is to be construed as.including a variable speed'wliich is synchronized withtn'e'fluctuationsf in speed of a second scanner or scanning drive motor.

A further advantage of the mechanism described above resides in the factthat the drum I is movable with respect to the scanning memher 6 exceptwhen actually transmitting or re cording and the drum may be actuallystopped during or even after the phasing operation without reouiringre-phasing of. the member 6.

While I have described in detail a preferred 7. embodiment of theinvention for the purpose of explaining the underlying principlesthereof, such description is only by way of illustration. Variousmodifications of the invention will occur to those skilled in the art,and may be made without departing from the scope thereof.

I claim:

1. In a telefacsimile machine provided with a rotatable scanning memberto be driven at predetermined speed and phase relation, in combination,motor means in direct driving relation to said scanning member tendingto drive the scanning member above synchronous speed, a rotatablephasing member, means including said phasing member for controlling theangular position of the scanning member in operation, means forsupporting said phasing member for rotation independent of said scanningmember, means for stopping the phasing member and for releasing the samefor rotation when a phasing pulse is received, a second motor meansoperating at synchronous speed'and connected to the rotatable phasingmember to maintain the rotative speed of the scanning member atsynchronous speed and a drive connection between said second synchronousmotor means and said phasing member embodying a pawl and a ratchet gearengaged thereby to allow rotation of the motor shaft when the phasingmember is stopped for phasing control, the teeth of said pawl and gearbeing shaped to provide a positive light driving torque from saidsynchronous motor means on the phasing member when it is released.

2. In a telefacsimile machine provided with a rotatable scanning memberto be driven at predetermined speed and phase relation, in combination,a motor which varies in speed in accordance with its load connected toand normally tending to drive said scanning member at a speed greaterthan the predetermined speed, a rotatable phasing member connected tosaid scanning member in such manner as to retard its speed when thephasing member and the scanner member have a predetermined phaserelationship, means for supporting the phasing member for rotationindependent of said scanning member, means for stopping the phasingmember and for releasing the same for rotation when a phasing pulse isreceived, thereby controlling the angular position of the scanningmember when the overdrive of the said member causes it to assume saidpredetermined phase relation to said phasing member, and means forcontinuously maintain ing the rotative speed of said phasing member atsaid predetermined speed during operation and thereby limiting therotation of the scanning member to such speed.

3. A facsimile driving and phasing mechanism according to claim 2 inwhich the means for maintaining the rotative speed of said phasingmember at said predetermined speed. comprises a synchronous motor gearedto the phasing member through an irreversible worm drive for limitingthe loading of said synchronous motor by the over-drive of thevariable-speed motor.

4. In a telefacsimile machine of the character described, incombination, a rotatable scanning member tending to rotate abovesynchronous speed, a rotatable phasing member connected to said scanningmember in such manner as to retard its speed when the scanning memberand phasing member have a predetermined phase relationship, means forsupporting said phasing member for rotation independent of the scanningmember, means for stopping the phasing member and for releasing the samefor rotation when a phasing pulse is received, thereby controlling theangular position of the scanning member when in said predetermined phaserelationship to said phasing member, and motor means for rotating thescanning member and for controlling the rotative speed of the phasingmember to obtain a predetermined synchronous speed thereof and of saidscanning member.

5. In a telefacsimile machine provided with a rotatable drum or scanningmember, in combination, a rotatable phasing member coaxial with the drumwhen the same is coupled to the phasing member and a pawl-and-ratchetdrive connection between the synchronous motor and said f phasing memberto permit the synchronous motor to run when the phasing member isstopped while retarding the phasing member to the speed of said motorwhen said member is released for rotation.

6. A driving mechanism for a facsimile ma chine according to claim 5 inwhich the drive connection consists of a pawl and ratchet gear havingteeth shaped to provide a light positive driving torque from thesynchronous motor to said phasing member and relatively heavy positiveretarding torque when the speed of the phasing member tends to exceedsynchronous speed.

'7. A driving mechanism for a facsimile machine according to claim 5 inwhich the phasing member is connected to the synchronous motor throughworm gearing in which the thread helix 1 angle of the teeth on thedriving worm of the motor is of the order of '7 to 12 degrees.

AUSTIN G. COOLEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Disclaimer 2,492,621.-Austin G. Cooley, New York,N. Y. FACSIMILE. SYNCHRONIZING DEVICE. Patent dated Dec. 27, 1949.Disclaimer filed Jan. 9, 1951,

by the assignee, Times Facsimile Corporation; the inventor consenting.

Hereby enters this disclaimer to claims 2 and 4: of said patent.

[Oficial Gazette F ebi'uarg 6, 1.951.]

